1. Field of the Invention
The present invention relates to an electrocatalyst and a method of manufacturing the same. More specifically, the present invention relates to an electrocatalyst prepared by a step of forming a reversed micellar solution which dissolves a catalyst component in micelles, a step of obtaining noble metal particles or complex metal particles by adding a reducing agent to the reversed micellar solution, and a step of loading the metal particles on a conductive support by mixing the conductive support into the reversed micellar solution.
2. Description of the Related Art
A hydrogen-oxygen fuel cell is classified into a variety of types in accordance with types of electrolytes, types of electrodes and the like. As typical fuel cells, there are ones of an alkaline type, a phosphoric acid type, a molten carbonate type, a solid electrolyte type, and a solid polymer type. Among them, the solid polymer fuel cell operatable at low temperature (usually, 100° C. or less) has gained attention, and in recent years, has been developed and put into practical use as a low-pollution power source for a vehicle.
As an electrocatalyst usable for such a fuel cell, there is one in which catalyst particles are loaded on carbon particles. Meanwhile, in order that such catalyst-loaded carbon particles may be far more widely used as the electrocatalyst of the fuel cell, it is necessary to minimize a usage amount of the catalyst by enhancing a utilization of the catalyst without lowering activity thereof, and to reduce a manufacturing cost of the catalyst by simplifying a manufacturing method thereof.
Heretofore, platinum-loaded carbon has been used in many fuel cells. In general, a method of manufacturing the platinum-loaded carbon is that a carbon support is added to a solution of chloroplatinic acid, a reducing agent is added to the precipitate to reduce the solution to platinum particles, and the platinum particles are adsorbed on the carbon support (refer to Japanese Patent Application Laid-Open No. H9-167622).
Meanwhile, in an oxygen reduction electrode for use in the fuel cell, oxygen reduction overvoltage is large, which is a main cause to lower efficiency of the fuel cell. For the electrocatalyst, noble metal such as platinum (Pt) and ruthenium (Ru) is used as a reaction catalyst for protons and oxygen. However, in such an electrocatalyst composed only of the noble metal, oxygen reduction activity is insufficient in some cases, and an oxygen reduction electrocatalyst that is high activity is required. An alloy or intermetallic compound of the noble metal, particularly Pt, and a base metal is known to exhibit an oxygen reduction activity higher than the electrocatalyst only of Pt, and it has also been proposed to use such a Pt-based alloy catalyst as the electrocatalyst for the fuel cell (refer to Japanese Patent Application Laid-Open No. S62-163746).